Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.83	13.758%	$69.199	$69.20	$69.20	$69.20
Purchase #2	$107.31	4.174%	$111.7891	$111.79	$111.80	$111.80
Purchase #3	$129.38	6.514%	$137.8078	$137.81	$137.80	$137.80
Purchase #4	$119.60	10.791%	$132.506	$132.51	$132.50	$132.50
Purchase #5	$30.28	10.290%	$33.3958	$33.40	$33.40	$33.40
Purchase #6	$196.52	5.563%	$207.4524	$207.45	$207.45	$207.50
Purchase #7	$65.47	11.266%	$72.8459	$72.85	$72.85	$72.80
7 purchase totals =	$709.39		$764.9960	$765.01	$765.00	$765.00